The objectives of this proposal are to understand the physiological role of enterostatin in the regulation of dietary fat consumption and to define the peripheral and central pathways through which enterostatin modulates this effect. There are distinct and independent peripheral and central systems that are responsive to enterostatin. We hypothesize that enterostatin released in the stomach or duodenum acts as a paracrine factor to activate an afferent vagal pathway which innervates the central systems to modulate fat intake in the immediate meal. Further, we hypothesize that enterostatin acts within the brain as a tonic signal to regulate fat appetite through inhibition of a kappa-opioidergic system that is activated by dietary fat intake. We shall use a variety of experimental strategies and techniques to investigate these hypotheses. We shall use Northern blots, confocal immunohistochemistry and an ELISA assay to study the subcellular distribution of enterostatin in relation to vagal terminals and the regulation of enterostatin synthesis and secretion in response to dietary fat. The effects of intraluminal and near-arterial infusions of enterostatin on food intake will be studied and the role of the afferent vagus in this response investigated. The role of serotonergic signals in the central response to enterostatin will be further studied using local microdialysis. The effects of dietary fat and enterostatin on kappa opioidergic systems will be investigated through study of their effects on receptor ligand binding, receptor mRNA levels and the levels of dynorphin protein in specific brain regions. Finally, we shall use a ligand binding approach to isolate the enterostatin receptor from brain membranes or neuroblastoma cells and investigate the distribution and regulation of this receptor activity. As a result of these studies, we shall gain important insight into the peripheral and central systems that affect fat intake. This new information will provide the exciting possibility of the development of a pharmacological approach to reducing fat appetite as a means to improving the health of the American population.